The present invention relates to a decentered optical system comprising a decentered lens and a decentered prism using a rotationally asymmetric surface, and an image display apparatus and an imaging apparatus using that decentered optical system.
So far, there has been a head-mounted type image display apparatus known that uses small-format display devices wherein original images on these display devices are enlarged by a viewing optical system to present them to a viewer. This head-mounted type image display apparatus is still required to decrease in the whole size and weight because of being mounted on the head for use. In order to impart a more realistic effect to the image presented, there is demand toward an optical system that can present the original image on the display device to the viewer at the widest possible angle of view and express it with high resolution.
One means for meeting such demand is embodied by an optical system for guiding a light beam from a display device into the viewer's eyeball, and it is especially effective for viewing at a wide angle of view that a prism optical system is located between the display device and the viewer's eyeball together with an optical element made up of two refracting surfaces or a so-called lens. For instance, JP(A)'s 2002-221688, 2002-244075, 2002-311378, 2002-318366, 2003-15041, 2010-92061 and 9-146036 disclose optical systems, each comprising a decentered prism combined with a refractive optical system (lens or the like).